Section switching process for railway systems with a long stator linear motor

ABSTRACT

The present invention relates to a method for switching over the current between successive stators of a railway system comprising a track and a vehicle and with a long-stator linear motor. The method according to the present invention proceeds from a conventional double-infeed step-change method. During the switching over of the current from one stator section of a long-stator winding phase to the following one, the section cable, which is assigned to the stator sections to be changed over and is supplied with power from two substations by double infeed, is split up. In this way, the sections to be changed over can be supplied by single infeed by a single substation in each case. It is possible thereby to avoid the unilateral loss of thrust which occurs in the case of conventional step-change methods.

FIELD OF THE INVENTION

The present invention relates to a method for section-changing forrailway systems having a long-stator linear motor.

BACKGROUND INFORMATION

In railway systems having long-stator linear motors, for examplemagnetic-levitation transport systems, the stator winding is arranged inthe form of at least one rail-like phase along the travel path or track.The secondary part, cooperating with the long stator, thus with theprimary part of a linear motor, and corresponding to the rotor of aconventional electric motor, is located on the vehicle, which movesalong the travel path. There are railway systems with only one windingphase. However, the subject matter of the present invention is railwaysystems in which there are two winding phases arranged in parallel. Forreasons of efficiency and of power requirements, the individual windingphases are usually subdivided into a plurality of stator sections(hereinafter referred to as sections) The individual sections areseperated from one another electrically and are supplied with currentonly when a vehicle travels over them. In order to permit continuousmovement of the vehicle along the travel path, the current must beswitched from a section no longer needed to the next following sectionof a winding phase. Because of the high voltages, this changeover of thesections must be effected at zero current. Switching over the currentfrom one section to the section following next in the direction oftravel is carried out in principle, such that initially the current ofthe presently active section is adjusted down, i.e., is reduced to zero.When the said section is in the currentless state, it is possible tochange over to the next section and then the current is adjusted upagain to its original value. Consequently, only a reduced thrust isavailable for driving the vehicle during the times of upward anddownward adjustment. The sections are completely de-energized during thechangeover or switch-actuating phase, so that no thrust at all isavailable. In order to avoid a complete loss of thrust, in the case ofthe railway systems under discussion, a second long stator or a secondwinding phase is present which is likewise subdivided into individualsections. The sections of the second winding phase are arranged offsetrelative to the sections of the first winding phase, so that thesectioning point between the successive sections of the one windingphase is overlapped by a section of the other respective winding phase.Various conventional section-changing methods are used for switchingover the driving current.

In the so-called three-step method, a total of three section cablesystems run along the travel path. The section cables of a drive regionof the travel path are supplied with current from one substation (singleinfeed) or from two substations (double infeed). The sections of awinding phase which are needed in each case to drive the vehicle arecontinuously electrically connected to the section cables. Normally,i.e., when no section change is to be made, only two mutually oppositesections of the one and of the other winding phase or, viewed in thedirection of travel, of the left and of the right winding phases, areactive. Before a vehicle travels over a sectioning point between twosuccessive sections, the section following the sectioning point isswitched in. Thus, during the section change, the full electric power orfull thrust is available. After the sectioning point has been traveledover, the section situated in advance of the sectioning point and nolonger needed to drive the vehicle is switched off again. Thedisadvantage of this method resides principally in the high "hardwareoutlay". Three section cables and at least three converters must beprovided in a substation. In another method, the so-calledalternating-step method, which is described in, for example, from thearticle entitled "Energieversorgung des Langstatorantriebs" (POWERSUPPLY OF THE LONG-STATOR DRIVE) in the journal "etz" volume 108 (1987)issue 9, pages 378 to 381, only two section cables are present. Since athird section cable is lacking, but three sections are simultaneouslytraveled over during the section change, one of the three sections mustalways remain de-energized, which leads to a maximum thrust dip of 100%of the winding phase affected. The cause of this thrust dip is thatduring the section change described above, the sections to be changedover are completely de-energized during the changeover phase, and onlythe section of the other winding phase which overlaps the sectioningpoint is active. This has a negative effect on traveling comfort in theform of jerking, and causes system fluctuations in the supply system ofthe substations.

It is an object of the invention to reduce the thrust dip when workingwith an alternating-step method.

The starting point in achieving the set objective was double-infeedrailway systems. In the case of double infeeding, the section cable of adrive region is supplied with power from two substations which arearranged at the ends of the section cable. A converter is present ineach substation for each section cable. The basic idea of the presentinvention consists in splitting a double-infeed section cableelectrically into two subphases during a section change, the onesubphase being supplied with power from one substation and the othersubphase being supplied from the other substation in single infeed. Atthe time of the section change, there is then a total of three voltagesources available for the three sections simultaneously being traveledover during a section change. Owing to the splitting up of the one cablesection, the two substations deliver only half the electric power to thetwo sections to be changed over (compared to the full power in the caseof double infeeding), with the result that in total only 150% of theelectric power or of the maximum possible thrust of 200% is available.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustration which depicts a simplified representationof a drive region of a travel path.

FIG. 2 shows a first step for a section change in accordance with thepresent invention.

FIG. 3 shows a second step for the section change in accordance with thepresent invention.

FIG. 4 shows a third step for the section change in accordance with thepresent invention.

FIG. 5 shows a fourth step for the section change in accordance with thepresent invention.

FIG. 6 shows a fifth step for the section change in accordance with thepresent invention.

FIG. 7 shows a sixth step for the section change in accordance with thepresent invention.

DETAILED DESCRIPTION

As shown in FIG. 1, a left winding phase L and a right winding phase Rare arranged along a travel path 1. Winding phases L and R aresubdivided into individual stator sections (hereinafter referred to as"sections"), AL_(n), AL_(n+1), . . . etc. and sections AR_(n), AR_(n+1).. . etc. which can be separately supplied with power. Two section cablesKL and KR are arranged along travel path 1. The said sections areconnected via connecting cables to the section cables assigned to them.These electrical connections can be interrupted in each case by a feedswitch. Sections AR of right winding phase R are offset by an offsetx_(v) with respect to sections AL of left winding phase L. Four of thefeed switches 2-5 are combined in each case to form a group in a commonswitching point. Each switching point is assigned a first pair ofsuccessive sections AL_(n), AL_(n+1) of the one winding phase L, and asecond pair of successive sections AR_(n) and AR_(n+1) of the otherwinding phase R that are arranged offset relative to the first pair. Twoswitching points S1 and S2 are shown by way of example in FIG. 1.Located in each switching point are four feed switches--feed switches 2,3, 4, 5 in switching point S1--feed switches 2, 3 being assigned to apair of successive sections AL_(n), AL_(n+1) of left winding phase L,and switches 4, 5 being assigned to a pair of successive sectionsAR_(n), AR_(n+1) of right winding phase R. Also located in the switchingpoints are coupler circuit-breakers 6, 7, by which section cables KL andKR can in each case be separated electrically into subphases TLa, TLb,TRa, TRb (as shown in FIG. 3). Arranged at the ends of section cables KLand KR are two substations UW 1, UW 2 which supply section cables KL andKR, or winding phases L and R assigned to them, with current along thelines of a double infeed.

The sequence of the method according to the invention may be seen fromFIGS. 2-7 and from diagram D1. For the sake of clarity, the componentsrequired for carrying out the method are provided with reference symbolsonly in FIGS. 1-2. The positions of a vehicle which are correlated witha specific method step are specified in diagram D1 by X1, X2, etc.

As shown in FIG. 2, before a vehicle F has reached a specific monitoredpoint X1 of the travel path which is situated in advance of sectioningpoint 8, the two sections AL_(n) and AR_(n), are supplied with current.Feed switches 2, 3 of switching point S1 are closed. Current can flowvia appropriate connecting lines from section cable KL to sectionAL_(n), and from section cable KR to section AR_(n). In this case, thecurrent is supplied in the manner of a double infeed from a converter(not shown) of substation UW 1 and a converter (not shown) of substationUW 2. In order to permit double infeeding, coupler circuit-breaker 6 insection cable KL is closed. The same holds true for couplercircuit-breaker 7 in section cable KR, into which substations UW 1 andUW 2 likewise feed current. The said sections are thus active. In eachcase, the vehicle is arranged with its entire length within the saidsections. The full thrust (2×100%=200%) is thus available for drivingthe vehicle.

Once the vehicle has reached point X1, the current of one substation, inthe present case substation UW 2, is adjusted down to the value zero.This operation is symbolized by arrow 9 in FIG. 2. The current in theother substation UW 1 remains unchanged. When adjusting the currentdownward, and later when adjusting it up, care is taken that a maximumpermissible jerk, i.e., a maximum permissible negative or positivechange in acceleration of the vehicle, is not exceeded (rate-of-changelimiting). Thus, compared to a conventional alternating-step method,none of the sections participating in the section change is switchedcompletely de-energized, but rather the current infeed is reduced onlyto 50% as long as the corresponding section is still interacting withthe vehicle. Consequently, there is only a thrust reduction of 50% inthe section affected, compared to a thrust reduction of 100% in the caseof the conventional alternating-step method. Since the secondtraveled-over section AR_(n) of winding phase R is fully activated, theoverall result at X2 is a thrust of the two sections AL_(n) and AR_(n)of 150%. As still to be shown, this value does not decrease during thefurther progress of the section change.

As the next method step, coupler circuit-breaker 6 is opened and sectioncable KL is electrically separated into two subphases TLa and TLb (shownin FIG. 3). Feed switch 4 is closed, as a result of which sectionAL_(n+1) is connected to substation UW 2 via subphase TLb. After theclosure of feed switch 4, the current in substation 2 is adjusted upagain to its original value (arrow 10 in FIG. 4). At the end of thisupward-adjustment operation, vehicle F has reached position X4. It isstill located with its entire vehicle length within section AL_(n),which is supplied with current via subphase TLa from substation UW 1(single infeed). On the other hand, section AL_(n+1) adjoiningsectioning point 8 is supplied in single infeed from substation UW 2.

In the further course, vehicle F shown in (FIG. 4) enters the area ofaction of section AL_(n+1) and leaves preceding section AL_(n) to thesame extent, there being a decrease in its vehicle length which isactive with respect to section AL_(n), and in its vehicle length whichis active with respect to section AL_(n+1). The thrust produced incooperation with section AL_(n) thus decreases continuously, and thethrust produced in cooperation with section AL_(n+1) increases steadily(compare subdiagram D 1.3). At point X5 or x_(m), at which half thevehicle has passed sectioning point 8, the said thrust components are ofthe same magnitude. Overall, the thrust remains constant when sectioningpoint 8 is traveled over. Together with the thrust, a total thrust oflikewise 150% results between X4 and X6 of section AR_(n).

When the vehicle has completely left section AL_(n) (position X6), thecurrent is adjusted down in substation UW 1. At the end of the downwardadjustment operation, section AL_(n) is de-energized. Vehicle F shown in(FIG. 5) is located with its rear end at position X7. Section AL_(n),which has become de-energized, is separated from subphase TLa by openingswitch 2, and coupler circuit-breaker 6 is closed (as shown in FIG. 6).Actuating the said switches takes a certain time, so that vehicle F isnow located with its rear end at position X8. The two subphases TLa andTLb are now connected to one another again. The current in substation 1is adjusted upward (symbolized by arrow 11 in FIG. 7). At the end ofthis upward adjustment operation, vehicle F is located with its rear endat position X9. Section AL_(n+1) is now supplied again from bothsubstations UW 1 and UW 2 (double infeeding). The two active sectionsAL_(n+1) and AR_(n) are fully activated, and consequently the fullthrust of 200% is effective again in each section (compare D 1.2 and D1.3).

A state has now been reached as at the start of the section change. Thesections which are to be changed over next are sections AR_(n) andAR_(n+1). To initiate the imminent section change, the convertersupplying section cable KR is driven down, that is to say the currentfed on the one side from substation UW 1 into section cable KR isreduced to zero. Next, coupler circuit-breaker 7 is opened and feedswitch 5 is closed. Section AR_(n+1) is then connected to substation UW2 via subphase TRb. A new section change can then begin, which proceedsanalogously to that described above.

The minimum section offset is to be seen in subdiagram D 1.2 or D 1.3.It results from segment x_(ges) and vehicle length 1^(Fa). Segmentx_(ges) is composed of sub-segments x_(R), x_(S) and x₁. Segment x_(R)is that segment which is traversed during the reduction, limited in rateof change, of the nominal thrust (segment between X1 and X2 as well asX8 and X9). Segments x_(s) are the paths which are covered during theswitching times, that is to say the actuating times of the switches.Finally, segments x₁ correspond to those segments which are coveredduring the times when the current in the substations is being controlledupward and downward.

A common feature of the alternating-step method according to the presentinvention and of the conventional alternating-step method is that at anyinstant of the section change, one section is not affected by thesection change. Thus, the idea suggests itself to use this section tocompensate for the loss in thrust of the sections to be changed over.One possibility for achieving such a thrust compensation would be tomake use of unneeded power reserves which are available, for example,when driving at a steady speed. However, this possibility forcompensating thrust has the disadvantage that, particularly during theacceleration phases--and generally in the case of a cost-optimizeddesign--virtually the entire installed converter power is required, andthen no current reserve is available for thrust compensation.

A further possibility consists in providing a power reserve by basicallynot using the entire converter current as long as no section change isperformed. Such a current reserve can be provided by using more powerfulconverters. However, this has the disadvantage of higher investmentcosts. A second possibility for providing a power reserve consists inreducing the nominal current in the case of a given converter powerwhile accepting a lowering of the thrust capacity between the sectionchanges. In the case of the conventional alternating-step method, asoutlined above, the loss in thrust is 100% in one winding phase. Theextra power required for thrust compensation in the corresponding otherwinding phase would therefore be 100%, that is to say 100% perconverter. Such a power reserve can be achieved either only by highinvestment costs or a reduction in the thrust capacity which is nolonger tolerable. Using an alternating-step method with mixed feedingaccording to the present invention, the loss in thrust during thesection change is only 50% in the winding phase affected. This meansthat the extra power to be made available is only 50%, which can, inaddition, be split between three instead of two remaining converters,that is to say the extra power per converter is only 33% instead of100%. Diagram D 2 relates to thrust compensation by reducing the nominalcurrent to 75% between the section changes. As can be seen fromsubdiagram D 2.3, during the section change (position X1 to positionX9), the current of section AR_(n), which is not affected by the sectionchange, is increased from 75% to 100%. Overall, this results in auniform thrust of 150% in total (subdiagram D 2.3). Given a lowering ofthe thrust capacity of only 25% in total, a uniform thrust as in thecase of a three-step method, and therefore optimum traveling comfort, isthus achieved. A further advantage is that flicker phenomena, i.e.fluctuations in current and power, are virtually prevented by theuniform system loading.

What is claimed is:
 1. A method for switching over a current betweensuccessive stator sectors of a stator winding of a railway system, therailway system including a long-stator linear motor, a vehicle and atravel path, the vehicle traveling along the travel path, the travelpath including a first stator winding phase and a second stator windingphase, the first stator winding phase and the second stator windingphase including sections, the sections of the second stator windingphase being offset relative to the sections of the first stator windingphase, comprising the steps of:a) assigning a first cable section to thefirst stator winding phase for supplying power to the first cablesection; b) assigning a second cable section to the second statorwinding phase for supplying power to the second cable section, each ofthe first cable section and the second cable section being separableinto two subphases via a circuit breaker; c) supplying current to afirst end of the first cable section and a first end of the second cablesection by a first substation; d) supplying current to a second end ofthe first cable section and a second end of the second cable section bya second substation; and e) performing a section change between a firstone of the sections of the first stator winding phase and a second oneof the sections of the first stator winding phase, the second one of thesections of the first stator winding phase being successive to the firstone of the sections of the first stator winding phase, wherein duringthe section change, one of the two subphases of the first cable sectionis electrically connected to the first one of the sections of the firststator winding phase, and another one of the two subphases of the firstcable section is electrically connected to the second one of thesections of the first stator winding phase.
 2. The method according toclaim 1, wherein the plurality of sections include stator sections. 3.The method according to claim 1, wherein the sections include individualwindings.
 4. The method according to claim 1, wherein stepe) furtherincludes the steps of: f) before the vehicle reaches a sectioning pointbetween a first one of the sections of the first stator winding phaseand a second one of the sections of the first stator winding phase,adjusting downward current supplied by the second substation; g) afterstep f), separating the first cable section into two subphases viaopening a circuit breaker, a first one of the two subphases beingelectrically connected to the first one of the sections of the firststator winding phase and carrying current, a second one of the twosubphases being electrically connected to the second one of the sectionsof the first stator winding phase and being deenergized; h) after stepg), adjusting upward current in the second substation; i) when thevehicle leaves the first one of the sections of the first stator windingphase, de-energizing the first one of the sections of the first statorwinding phase by adjusting downward current supplied by the firstsubstation; j) after step i), electrically joining the two subphases ofthe first cable section by closing the circuit breaker; and k) afterstep j), adjusting upward current supplied by the first substation; andl) during an entire duration of step e), supplying one of the sectionsof the second stator winding phase with current from both the firstsubstation and the second substation, the one of the sections of thesecond stator winding phase being arranged offset relative to the firstone of the sections of the first stator winding phase and the second oneof the sections of the first stator winding phase.
 5. The methodaccording to claim 4, wherein step h) is completed one of at and beforea time when a front end of the vehicle has reached the sectioning point.6. The method according to claim 1, further comprising the stepsof:assigning the first one of the sections of the first stator windingphase, the second one of the sections of the first winding phase, theone of the sections of the second stator winding phase, and a second oneof the sections of the second stator winding phase a common switchingpoint, the common switching point including two coupler circuit breakersassigned to the first section cable and the second section cable, andfurther including four feed switches for controlling an infeed ofcurrent into the first one of the sections of the first stator windingphase, the second one of the sections of the first winding phase, theone of the sections of the second stator winding phase, and the secondone of the sections of the second stator winding phase, the first one ofthe sections of the second winding phase and the second one of thesections of the second winding phase being offset relative to the firstone of the sections of the first winding phase and the second one of thesections of the first winding phase.
 7. The method according to claim 1,wherein the first one of the sections of the first stator winding phaseand the second one of the sections of the first stator winding phase areoffset from a first one of the of the sections of the second statorwinding phase and a second one of the sections of the second statorwinding phase by more than a length of the vehicle.
 8. The methodaccording to claim 7, wherein the first one of the sections of the firststator winding phase and the second one of the sections of the firststator winding phase are offset from a first one of the of the sectionsof the second stator winding phase and a second one of the sections ofthe second stator winding phase by as least as a much as a sum of thelength of the vehicle and a length of sections traversed at apredetermined speed by the vehicle during the upward and downwardadjustment of the current and during switch actuating times.
 9. Themethod according to claim 1, further comprising the steps of:applying areduced nominal current to the sections of the first winding phase andthe sections of the second winding phase between section changes to forma power reserve; and increasing a thrust component of at least onesection of the sections of the first and second winding phases during asection change using the power reserve, the at least one section beingcurrentless.
 10. The method according to claim 9, wherein the nominalcurrent is reduced to 75% between the section changes.